Conventionally, inspecting and managing air pressure of tires mounted on vehicles has been desirable from the perspectives of enhancing tire durability, wear resistance, fuel economy, riding comfort, and driving performance. Therefore, various systems for monitoring air pressure of tires have been proposed. Generally, in these systems, air pressure in tires is monitored by detecting the air pressure information of a tire assembled on a wheel, providing a transmitting device for transmitting this information in a tire cavity region of each wheel, and acquiring the air pressure information of each tire from the transmitting devices.
Puncture repair liquid to be injected within the tire cavity region interposed between the tire and the rim is often used when a puncture occurs in a tire. Since the puncture repair liquid is in a liquid form, the puncture repair liquid adheres to the inner surface of the tire that faces the tire cavity region and may even adhere to the transmitting device provided in the tire cavity region when the puncture repair liquid is injected into the tire cavity region. In some cases, the puncture repair liquid solidifies and covers an opening provided in the transmitting device, thus becoming a problem that adversely affects the measurement of the air pressure.
To solve this problem, a wheel condition detecting device that can prevent the ingress of foreign material from a communicating portion for detection, and maintain normal detecting status has been proposed (Japanese Unexamined Patent Application Publication No. 2008-62730A).
Specifically, a communicating portion opening and closing mechanism that opens and closes a communication hole provided in a case is provided on the valve in a tire pressure monitoring system (TPMS) of a wheel condition detecting device. When repairing a puncture, the puncture repair liquid is prevented from penetrating into the detection space through the communication hole. This communicating portion opening and closing mechanism is configured so as to include a mechanical mechanism containing a lid body and a screw coil spring, and the communication hole is automatically opened and closed by centrifugal force that acts on a wheel.
Also, a transmitting device that is capable of appropriately detecting and transmitting tire information such as tire air pressure information and the like and a tire information monitoring system that is capable of determining whether or not there is an abnormality in the tire, even when the puncture has been repaired using puncture repair liquid, are known (Japanese Unexamined Patent Application Publication No. 2010-150941A).
The transmitting device includes a sensor that detects the condition of the air filling the tire cavity region as tire information, a transmitter that wirelessly transmits the detected tire information, and a wall that covers the sensor and transmitter. A housing provides an internal space partitioned from the tire cavity region by the wall of the housing. A ventilation hole is provided in the housing that penetrates the wall and communicates to internal space and the tire cavity region. In this case, the opening area of the ventilation hole on the surface of the housing facing the tire cavity region is not more than 0.4 mm2, and the opening area of the inside opening part of the ventilation hole on the surface of the housing facing the internal space is larger compared with that of the outside opening part.
However, the communicating portion opening and closing mechanism of the wheel condition detecting device as described above is configured from a mechanical mechanism that includes a lid and a screw coil spring, so there is a problem that the device itself is complex, and expensive.
On the other hand, in the transmitting device of the tire information monitoring system, even if a puncture has been repaired using puncture repair liquid, it is still possible to appropriately detect the tire information such as the tire air pressure information and the like, but the opening area of the outside opening part is not more than 0.4 mm2, so precise and accurate processing is necessary.